Adhesive closures for bags, such as thin plastic sandwich bags, have been widely used. A transverse adhesive streak near the mouth of a sandwich bag is generally preferred for this purpose. However, a streak of exposed and unprotected adhesive adjacent to the mouth of such a bag structure has presented many drawbacks. When these bags are packaged within a dispensing carton, either in continuous roll form or individually adjacent to one another, the bags have a tendency to stick to one another as well as to exterior objects following dispensing of individual bags from the container, thus making it difficult to utilize the bags. In addition, the adhesives which are used are necessarily ralatively non-aggressive in an attempt to alleviate such problems, thereby making the closures less effective than would otherwise be possible.
An improved Z-fold adhesive striped closure has been described in U.S. Pat. No. 3,990,627 for protecting an adhesive streak extending across the front wall flap of a small bag, such as a sandwich bag. A fast and simple method and apparatus for making such Z-folds or pleats in a continuously advancing sheet is needed, however, particularly in the manufacture of sandwich bags which are serially connected in roll form by a perforated or weakened structure.
An additional device of the prior art has long been used for closing large plastic bags, such as trash bags. This device is a flexible strip of material such as paper, enclosing a bendable piece of metal wire. Such strips are commonly placed in the box of trash bags as an easily ruptured sheet or are adhesively attached to each bag by a piece of tape.
However, it would be far preferable to have each strip as an integral part of the bag structure. A convenient means for doing so is an adhesively secured pleat within which the closure strip is disposed, but no method or apparatus is available for forming such a pleat and placing the strip therein. Similarly, a drawstring can be placed within a pleat for subsequently closing the mouth of a bag by pulling upon both ends of the drawstring and then tying it.
A third area of interest in the prior art is the opening of plastic bags and other containers, such as foil-laminated bags for food products, shipping bags for fertilizer, animal feed and the like. Many of the bags are so tough and difficult to open that a piece of wire or string is sometimes attached to the bag structure to serve as a cutting tool. However, using the wire or string for its intended purpose is not always easy. A simple and reliable device for incorporating the wire or string into the bag structure and for readily using it to open the bag by slicing through the sheet material thereof would be a distinct advance in the art. A pleat enclosing the cutting material would provide this structure, but again the prior art provides no method or apparatus therefor.